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Getting/changing class of an element with other elements in it. JavaScript/JQuery

I made a blog archive in the format of this:
+Year
+Month
Title
Sample code:
<ul>
<span class="toggle">+</span>
<li class="year">$year
<ul>
<span class="toggle">+</span>
<li class="month active">$month
<ul>
<li class="title active">$title</li>
</ul>
</li>
</ul>
</li>
</ul>
I used $(this).next().toggle(), which works fine toggling the lists, but the entire list is expanded in the beginning when the page loads, and I don't want that.
So I changed to changing class names (active/inactive). I want to change the class of the month/title lists to inactive and back when the + span is clicked. The problem is using $(this).next() doesn't work.
If I try $(this).next().hasClass("active");
It will return a false. Or console.log($(this).next().attr("class"));, which gives undefined.
$(this).next().html(); gives:
<li class="month active"><span class="toggle">+</span><ul><li class="title active">...</li></ul></li></ul></li></ul>
The very next thing that follows the + span is the list with class of active, but it doesn't recognize the class? I don't understand why .toggle() works, but this doesn't.
What option do I have to make this work?

The idea is to capture the click event on the span class and toggle active/inactive on the year so that it shows correctly. Here's some psuedo code:
$('.toggle').on('click', function(){
$(this).next().toggleClass('active').toggleClass('inactive');
});
This will only work if the element has a class of inactive on page load, like this:
<ul>
<span class="toggle">+</span>
<li class="year inactive">$year
<ul>
<span class="toggle">+</span>
<li class="month active">$month
<ul>
<li class="title active">$title</li>
</ul>
</li>
</ul>
</li>
</ul>

When you had your initial toggle working but it displayed the items on load, you could have set the next element (the unordered list) to
style="display: none"
As for
console.log($(this).next().attr("class");
You are missing a parenthesis:
console.log( $(this).next().attr("class") );

Hope this helps.
By using little bit of CSS and toggling the class of ul to active only on click will fix your issue. Below is a working example.
$('.toggle').on('click', function() {
$(this).parent().toggleClass('active');
});
ul {
list-style-type: none;
}
ul:not(#MainNode) {
display: none;
}
ul.active > li > ul {
display: block !important;
}
.toggle {
cursor: pointer
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="MainNode">
<span class="toggle">+</span>
<li class="year">Year
<ul>
<span class="toggle">+</span>
<li class="month active">Month
<ul>
<li class="title active">Title</li>
</ul>
</li>
</ul>
</li>
</ul>

Remove the class of one element and assign it to another using JavaScript

I need to remove the selected class of an <a> and assign it the last <a> instead. Both are nested within individual <li> elements.
Here's an example of the code:
<ul class="tabs clearfix">
<li class="tab">Home</li>
<li class="tab">About</li>
<li class="tab">Profile</li>
<li class="tab">History</li>
<li class="tab">The Beginning of V-Cube</li>
</ul>
How can I achieve this using JavaScript/jQuery? Please advise.
EDIT:
Let's say I don't want to target the last tab specifically. Can the href be used as a selector instead?
EDIT #2:
Thank you so much everyone for the quick response. All your answers were spot on, wish I could mark them all as answers :)

To remove class from an element, use removeClass.
To get the last element, use :last selector or last(). To add new class to element use addClass
$('.selected').removeClass('selected');
$('.tabs li:last a').addClass('selected');
// OR
// $('.tabs li').last().children('a').addClass('selected');
.selected {
color: green;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<ul class="tabs clearfix">
<li class="tab">Home
</li>
<li class="tab">About
</li>
<li class="tab">Profile
</li>
<li class="tab">History
</li>
<li class="tab">The Beginning of V-Cube
</li>
</ul>
Update
Let's say I don't want to target the last tab specifically. Can the href be used as a selector instead?
$('.tabs a[href="#five"]').addClass('selected');

Try this.
$(".tabs li").first().find("a").removeClass("selected");
$(".tabs li").last().find("a").addClass("selected");
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul class="tabs clearfix">
<li class="tab">Home</li>
<li class="tab">About</li>
<li class="tab">Profile</li>
<li class="tab">History</li>
<li class="tab">The Beginning of V-Cube</li>
</ul>

Try this:
$(document).ready(function(){
var classname = $(".tabs li:first-child a").attr("class");
console.log(classname);
$(".tabs li:last-child a").addClass(classname);
$(".tabs li:first-child a").removeClass();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<ul class="tabs clearfix">
<li class="tab">Home</li>
<li class="tab">About</li>
<li class="tab">Profile</li>
<li class="tab">History</li>
<li class="tab">The Beginning of V-Cube</li>
</ul>

it is quite easy also in vanilla JS:
document.querySelector('.selected').classList.remove('selected');
document.querySelector('.tabs li:last a').classList.add('selected');
If you want to use an arbitrary a and select the attribute href then you should use this selector:
a[href="HREFVALUE"]

$('.clearfix').find('.selected').removeClass('selected');
$('.clearfix').find('li:last').find('a').addClass('selected');
$("a[href$='five']").addClass('bold');
.selected {
color: red
}
.bold {
font-weight: bold
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<ul class="tabs clearfix">
<li class="tab">Home
</li>
<li class="tab">About
</li>
<li class="tab">Profile
</li>
<li class="tab">History
</li>
<li class="tab">The Beginning of V-Cube
</li>
</ul>
Just use .removeClass() and .addClass()
.removeClass()
Remove a single class, multiple classes, or all classes from each element in the set of matched elements.
.addClass()
Description: Adds the specified class(es) to each element in the set of matched elements.

Jquery If class has matching ID then hide

What I'm trying to do here is check if an element has the same id as a class in another element if so hide the matching id.
So far this is what I have came up with but it doesn't seem to kick.
JSfiddle
var theid = $('#me li').attr('id');
if ($('#you li').hasClass( theid )) {
$('#me li#'+theid+'').hide();
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<ul id="me">
<li id="num-0">iam 1</li>
<li id="num-1">ieam 2 & should be hidden</li>
<li id="num-2">iam 3</li>
<li id="num-3">iam 4</li>
<li id="num-4">ieam 5 & should be hidden</li>
<li id="num-5">iam 6</li>
</ul>
<ul id="you">
<li class="num-1">iam killer</li>
<li class="num-4">iam killer</li>
</ul>

Use each() to loop over all the li elements inside the #you
hide() the elements having the id same as the class of current element in loop.
$('#you li').each(function() {
$('#' + $(this).attr('class')).hide();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<ul id="me">
<li id="num-0">iam 1</li>
<li id="num-1">ieam 2</li>
<li id="num-2">iam 3 & should be hidden</li>
<li id="num-3">iam 4</li>
<li id="num-4">ieam 5 & should be hidden</li>
<li id="num-5">iam 6</li>
</ul>
<ul id="you">
<li class="num-2">iam killer</li>
<li class="num-4">iam killer</li>
</ul>
Demo

When you use the .attr() method on a jQuery object that contains multiple elements, it just returns the attribute from the first element. You need to loop over each element and check them one at a time.
It is, however, OK for your purposes to use .hasClass() on the set of all of the #you elements, because .hasClass() will return true if any of the elements in the set has that class. So:
var you = $('#you li');
$('#me li').each(function() {
if (you.hasClass(this.id))
$(this).hide();
});
Note that I'm keeping a reference to the $('#you li') jQuery object in the variable you to save selecting those elements again every time in the loop.
Demo: https://jsfiddle.net/d65sz4js/2/

Try this for your jquery:
$(function() {
$("#you li").each(function(){
var theid = $(this).attr('class');
$('#'+theid).hide();
});
});
Demo: https://jsfiddle.net/nkem9o7o/

You could filter the #me li's, returning elements where their id exists as a class in #you li's, then just hide them. This would also work for multiple classes:
$('#me li').filter(function() {
return $('#you').has('.' + this.id).length;
}).hide();
Here's a fiddle

Find all next elements with specific class

I have html like this:
<ul>
<li class="foo">One</li>
<li class="bar">Two</li>
<li class="bar">Tree</li>
<li class="bar">Four</li>
<li class="foo">Five</li>
<li class="bar">Six</li>
<li class="bar">Seven</li>
</ul>
and I have JS code like this:
$('.foo').click(function() {
$(this).allNext('.bar');
});
How can I select all elements that are after .foo and have class bar.

You can use nextAll:
$('.foo').click(function() {
$(this).nextAll('.bar');
});

beside nextAll may be you want to know about nextUntil() .. it will select all .bar until the next .foo
$('.foo').click(function() {
$(this).nextUntil('.foo').css('background','red');
});
DEMO

Making parent link unclickable in a drop-down menu with jQuery

I have a drop-down menu that are dynamically added through WordPress. It looks like this:
Pictures
Sea
Forest
City
"Sea", "Forest" and "City" is categories with "Pictures" as parent category.
My question is:
How do I make the "Pictures" category unclickable?
I did this with jQuery:
$(document).ready(function(){
//Make parent links unclickable
$(".page-item-3").click(function(){
return false;
});
});
...and this with CSS:
li.page-item-3 a {
cursor:default;
}
.page-item-3 ul li a {
cursor: pointer;
}
Markup looks like this:
<div id="menu" class="jqueryslidemenu">
<ul>
<li class="cat-item cat-item-1 current_page_item">Blabla</li>
<li class="page_item page-item-2">Blabla
<ul>
<li class="page_item page-item-28">Blabla</li>
<li class="page_item page-item-30">Blabla</li>
<li class="page_item page-item-39">Blabla</li>
</ul>
</li>
<li class="page_item page-item-3">Blabla
<ul>
<li class="page_item page-item-5">Blabla 1</li>
<li class="page_item page-item-7">Blabla 2</li>
<li class="page_item page-item-9">Blabla 3</li>
<li class="page_item page-item-11">Blabla 4</li>
<li class="page_item page-item-13">Blabla 5</li>
</ul>
</li>
<li class="page_item page-item-15">Blabla
<ul>
<li class="page_item page-item-222">Blabla</li>
<li class="page_item page-item-224">Blabla</li>
<li class="page_item page-item-226">Blabla</li>
</ul>
</li>
<li class="page_item page-item-17">Blabla</li>
<li class="page_item page-item-36">Blabla</li>
</ul>
</div>
This almost works But the jQuery code makes all the drop-down links unclickable too.
It would be great if anyone knows how to remove the status bar url while hover the "Pictures" link. But I don't think that is possible to make in moderns browsers such as Safari och Firefox?
Thanks!

I don't know what control you have because of Wordpress but you're having this problem because everything is contained in the title list item (page-item-3) and you're cancelling the click on this item. If you can apply a class to the title link itself, you can apply the jQuery to that directly.
Unfortunately you can't say ".page-item-3 a" because this apply to all links in the list.
Re-Edit - This should select the first link in the list and cancel the click value of that. You may need to apply this for each 'title' link you have.
$(".page-item-3 a:first").click(function() {
return false;
}

$(".page-item-3").children("a").click(function(e) {
e.preventDefault();
});
*****or with CSS*****
.unclickable {
z-index:-1;
}
$(".page-item-3").children("a").addClass("unclickable");

just replace the href attribute value with #. That way when the user clicks on it, the page goes to #, which is the same page they are on, and nothing happens. Keep the CSS you wrote so the hand pointer does not appear when they hover it, but remove the jQuery code.
Using jQuery:
$(".page-item-3>a").attr("href", "#")

Try this:
$(document).ready(function(){
//Make parent links unclickable
$("div > ul > li > a").click(function(){
return false;
});
});
This will disable all the first links in your list without needing the class name.

I use this :
$j = jQuery.noConflict();
$j(document).ready(function(){
//Make parent links unclickable
$j("div[id='nav'] > ul > li > a ").removeAttr("href");
});